Dr Ray O’Connor takes a look at recent clinical papers on diet and nutrition, and how, amongst other findings, adherence to a plant-based diet is associated with lower obesity rates
The food system significantly affects the environment through land use, emissions from livestock, deforestation, and food waste. Diet sustainability considers the environmental effects of food production, distribution, and consumption. Animal products emit more greenhouse gases than plant-based foods, prompting a shift towards plant-focused diets for reduced emissions. Sustainable diets prioritize plant based foods, adjusting for regional eating habits.
Dr Ray O’Connor
These diets aim to be both environmentally friendly and conducive to human health, addressing concerns like obesity and chronic diseases. Obesity is a major global health challenge, and its complex relationship with food production and consumption patterns calls for sustainable solutions to reduce pressure on ecosystems and promote healthier lifestyles.
Tackling obesity requires holistic strategies that address not only individual health but also the broader environmental impacts of food systems. This systematic review1 examined the link between plant-based diets and obesity focusing on studies assessing Body Mass Index (BMI) and body fat assessment.
The authors included original articles written in English with participants aged ≥18 years and a prospective longitudinal or randomized controlled study design. They included studies assessing the effects of a plant-based diet according to the ‘EATLancet’ model and/or giving details on portions and frequencies of plant-based protein sources and the level of food processing. They excluded definite dietary patterns (e.g. Dietary Approaches to Stop Hypertension – DASH – vegetarian diet, vegan diet, Mediterranean, Nordish, etc.).
Their conclusion was that, despite limited research, evidence suggests that adherence to a plant-based diet, particularly a healthy one, is associated with lower obesity rates. They recommend that more longitudinal and intervention studies are necessary for a stronger consensus on the matter.
In 2025, the US Food and Drug Administration (FDA) proposed a mandatory single front-of-package label (FOPL) listing low, medium, or high descriptors and the percent Daily Value (%DV) for saturated fat, sodium, and added sugars. Effects of this scheme (referred to as Nutrition-Info-%DV) on consumer understanding, perceptions, and behaviours are unknown. This was an online randomised controlled trial2 which aimed to compare the FDA’s proposed label against potential alternatives.
The authors recruited a national sample of US adults aged 18 years or older who reflected US demographics. Participants were randomly assigned to view products labelled according to one of five conditions: (1) a no-label control; (2) the FDA’s proposed scheme (Nutrition-Info-%DV); (3) a Nutrition-Info scheme with no %DV and High highlighted in red (Nutrition-Info-Red); (4) a single label scheme listing all nutrients contained in a high amount (High-In); or (5) a multilabel scheme with separate labels for each nutrient contained in a high amount (Multi-High-In).
Participants were masked to the study objectives. Primary outcomes included consumer understanding (ie, correct identification of products with the healthiest and least healthy nutrient profiles, correct assessment of high nutrient content) and perceived healthfulness of unhealthy products (high in one, low in two nutrients). A total of 15,582 participants were randomly assigned and after certain exclusions an analytical sample of 13,929 (7,021 [50 per cent] women, 6,851 (49 per cent) men.
All FOPLs improved consumer understanding compared with the control. The authors’ conclusion was that FOPLs that only highlight high amounts of nutrients of concern, like Multi-High-In, outperformed the FDA’s proposed scheme and should be considered for implementation to help consumers quickly identify and make healthier dietary choices.
Another aspect of weight loss theory is the concept of intermittent fasting. Does it help bring about weight loss? This was the topic of a recent Cochrane review.3 The objective was to evaluate the benefits and harms of intermittent fasting versus regular dietary advice, no intervention or waiting list for adults with overweight or obesity.
The authors searched CENTRAL, MEDLINE (Ovid), and two trials registers up to November 5, 2024, as well as reference checking, citation searching and contact with study authors to identify additional studies. They included randomised controlled trials (RCTs) and cluster-RCTs that compared intermittent fasting (including time-restricted feeding, periodic fasting, alternate-day fasting, and modified alternate-day fasting) with regular dietary advice, no intervention or waiting list in men and women with overweight or obesity, with or without associated comorbid conditions.
The minimum duration of the intervention was four weeks, and the minimum duration of follow-up was six months. The results were disappointing. The authors concluded that, compared to no intervention or waiting list, intermittent fasting likely results in little to no difference in weight loss and may result in little to no difference in quality of life or adverse events, but the evidence is very uncertain.
Would a food tax help improve a population’s diet? Fiscal food policies can improve diets and reduce the burden of diet-related diseases. The aim of this modelling study4 was to model the effects of various health-promoting food taxes and subsidies in Australia on health, economics, and equity. The modelled scenarios included a 20% tax on unhealthy foods (ie, sugar-sweetened beverages, confectionery, snack foods, biscuits, pastries, ice cream, and processed meat), a 20 per cent subsidy for fruits and vegetables, and a 20 per cent tax on unhealthy foods earmarked to subsidise fruits and vegetables.
The authors used a food demand system and nationally representative dietary intake data from the National Nutrition and Physical Activity Survey to estimate changes in energy, sodium, fruit, and vegetable intake for each policy across five-year age–sex–socioeconomic status groups.
The findings were interesting. The authors estimated that a 20 per cent tax on unhealthy foods could avert 212,000 premature deaths, generate 1,370,000 Health Adjusted Life Years (HALYs), lower health-care costs by AU$14·9 billion, and promote health equity. The estimated HALYs gained could be approximately seven times greater than by taxing sugar-sweetened beverages alone. The authors concluded that fiscal food policies could be powerful levers to promote health and equity in Australia and should be considered by policy makers.
References:
- Mambrini S et al. Plant-based and sustainable diet: A systematic review of its impact on obesity. Obesity Reviews. 2025;26:e13901. https://doi.org/10.1111/obr.13901
- Lemmon B et al. Efficacy of front-of-package nutrient labels designed for mandatory implementation in the USA: an online randomised controlled trial. Lancet Public Health 2026; 11: e221–32. DOI: 10.1016/S2468-2667(26)00027-7.
- Garegnani L et al. Intermittent fasting for adults with overweight or obesity. Cochrane Database of Systematic Reviews 2026, Issue 2. Art. No.: CD015610. DOI:10.1002/14651858.CD015610.pub2
- Davies T et al. Estimated effects of food taxes and subsidies on health, economics, and equity in Australia: a modelling study. Lancet Public Health 2026; 11: e212–20. DOI: 10.1016/S2468-2667(26)00043-5